Selective photographic hardening



' LEONARD T. 'IRQLAND, OF MALDEN, MASSACHUSETTS, ASSIGINOB T KALMUS,

' tion, whereby the other Patented Apr. 28, 1925.

I 1,535,700 UNITED STATES'PATENT OFFICE- COH- strocx & wnsoo'r'r me, or:eos'ron, MASSACHUSETTS, A CORPORATION OF mAssA- onosn'r'rs.

snnn'c'rrvr. iHOTOGBAPHIC HABDENING.

NO Drawing.

To all whom it may concern:

Be it known that LEONARD T. TROLAND, a citizen of the United States, andresident of Malden, in the county of Middlesex and State ofMassachusetts, has invented new' and useful Improvements in SelectivePhotographic Hardening, of which the following is a specification.

This invention relates to the selective treatment of the exposed andunexposed portions of light-sensitive films by which one of theportions, for example the exposed portion, is made harder than the otherporthe two portions react differently to subsequent treatment, as forexample a hot water etch in which the relatively soft portion isdissolved oii leaving portion in relief or a dye bath in which the dyeis"; absorbed predominately by one portion.

It has been proposed to efiect this selective hardening in thedeveloping process by employing a pyro developer comprising pyrogallicacid and an accelerator such as sodium hydroxide or ammonium hydroxide.However, such developers have proved unsatisfactory, particularly in theproduction of motion picture film where a high degree of perfection anduniformity *is required, owing to their inherent tendencies to hardenthe unexposed as well as the exposed ortions, to vary fromtime to timein tieir action, to leave the exposed portions more or less For example,the princi al objection to a developer containing so ium hydroxide isits strong tendency to harden the unexposed as well as the ex osedportions of the film; and the chief ob ection to the use of ammofriable,to produce chemical fog, etc.

nium hydroxide, particularly in developing motion ieture film, is thedifficulty of securin uni orm results in successive mixtures, this beinglargely due tothe strong tendency of ammonium hydroxide to lose strengthby evaporation when in the concentrated condition in which it is keptprior to mixing with the developer.

Objects of the invention are to provide a film treatin .com osition andmethod by which the a oresai selective hardening may be effectedthroughout long series of images with uniformit to restrict thehardening to one of the, a oresaid portions of the film,

to make the hardened portion of the film firmer and less friable, toreduce the chemi- 1 Application filed September 13, 1922. Serial No.588,086.

cal fogging action of the com osition, to

increase the speed of action of t e composition without substantiallyaffecting the quality-of the action, and to produce relief images whichare more sharply etched and WhlCll are less likely to become scratchedor otherwise mutilated'in production or in subsequent use.

According to the resent invention the developer and/or har enincomposition is prepared by mixing with a eveloper and/or hardener suchas pyrogallic acid or other suitable polyhydroxybenzene, a fixed alkaliaccelerator such as sodium hydroxide and a salt of a relatively weakalkali, such as ammonium chloride orbromide or other halide.

The admixture of the salt of a weak base eliminates the objectionableeii'ectsof the fixed alkali accelerator which have heretofore renderedits use unsatisfactory. Instead of hardening the'light-sensitive filmmore or less throughout, as pyro developers containing fixed alkaliaccelerators have heretofore done unless employed with a restrainer suchas sodium sulphite, the fixed alkali and alkali halide product isnotably free from this tendency. Moreover, in making relief images byetching 011' the unexposed portion of the film, the soft and delicatenature of the reliefs made with a hardener cont ining 'sulphite isavoided with this developer which 'ields exceptionally firm reliefs' andthe re 'efs are much more sharply defined, esfpecially in machine 0eration, than relie s produced by an or inary pyro-ammonia developer.

A small amount of citric acid may be incorporated in the pyro stocksolution for its preservative action on the solution before thedeveloper is mixed. As is customary, potassium bromide may be added tothe mixture to restrain fog, but as above stated one of theadvantages ofthe fixed alkali and halide of a weak base combination is that it hasthis function. .'A satisfactory formula for use in developing andhardening motion picture film in a continuous machine is as follows:pyrogallic acid .82 gms, citric acid, .02 gms, tassium bromide .40 gms,sodium hydroxi e .34 gms, ammonium chloride .17 gms, and enough water tomake a total of 100 c. c.

The sodium hydroxide and ammonium chloride react to some extent to formsodium chloride and ammonium hydroxide;

and better results seem to be attained by separately adding the sodiumhydroxide and ammonium chloride just before use.-

The preferred method of mixing is to mix the pyro in water, then mix inthe chloride, and then add the sodium hydroxide.

To make relief positives with positive stock having therein a yellow dyeas disclosed in the applications of Eastman A, Weaver Serial No. 512,300and Serial No. 512,391, filed November 2, 1921, the development shouldbe carried on for about two minutes at a temperature of F. and thetemperature of the etch Water should be about 130 F.

This developer has the desirable characteristics of both the well-knownpyro-soda and pyroamnionia developers Without the undesirablecharacteristics of either. It has the uniformity and reliability ofpyro-soda, and the selectivity in hardening of pyroammonia; at the sametime it produces less chemical fog than pyro-ammonia so that thedeveloper may be made stron er and the development more complete, an itdoes not tend to harden the unexposed portions of the emulsion as doespyro-soda. Moreover, this developer seems to be unique in that itproduces firmer, sharper, less delicate and less friable reliefs.

This developer eliminates the use of a restrainer such as sodiumsulphite which is easily oxidized and unreliable in action and which hasa softening effect upon the reliefs, making all the gelatine spongy. Theprobable explanation of this marked difference in results is that thesulphite developer restrains the hardeningaction throughout both theexposed and unexposed portions Whereas the developer herein claimedavoids any tendency to harden in the unexposed portion inasmuch as itavoids chemical fogmg. -VVhat I claim:

1. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a hardener forhardening one of said portions, a fixed alkali accelerator and a salt ofa weak base.

2. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a developeradapted to harden one of said portions, a fixed alkali accelerator, anda halide of a weak base.

3. Acomposition for treating light-sensitive film having exposed andunexposed portions which is constizuted essentially of apolyhydroxybenzene, a fixed alkali accelerator, and a halide of a weakbase.

4. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a developeradapted to harden the exposed portions, a fixed alkali accelerator, andan ammonium halide.

5. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of apolyhydroxybenzene developer, a fixed alkali accelerator, and ammoniumchloride.

6. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a hardener forhardening one of said portions, sodium hydroxide and a salt of a weakbase.

7. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a developeradapted to harden one of said portions, sodium hydroxide and a halide ofa weak base.

8. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of apolyhydroxybenzene, sodium hydroxide and a halide of. a weak base.

9. A composition for treating light-sensitive film having exposed andunexposed portions which is constituted essentially of a developeradapted to harden the exposed portions, sodium hydroxide and an ammoniumhalide.

10. A composition for treating lightsensitive film having exposed andunexposed portions which is constituted essentially of apolyhydroxybenzene developer, sodium hydroxide and ammonium chloride.

11. The art of treating light-sensitive film having exposed andrelatively unexposed portions which comprises mixing with a developerWhose oxidization product is a hardener, a fixed alkali and a salt of aWeak base in such proportions as to convert the fixed alkali at least inpart into an accelerator having less tendency to harden one of saidportions of the film, and hardening the othe of said portions of thefilm with the mixture.

12. The artof treating light-sensitive film having exposed andrelatively unexposed portions which comprises mixing with apolyhydroxybenzene, a fixed alkali and a halide of a weak base in suchproportions as to convert the fixed alkali at least in part into anaccelerator having less tendency to harden the unexposed portions of thefilm, and hardening the exposed portions of the film with the mixture.

13. The art of treating light-sensitive film having exposed andrelatively unexposed portions which comprises mixing with a developeradapted to harden the exposed portion, sodium hydroxide and a halide ofa weak base in such proportions as to convert the sodium hydroxide atleast in part into an accelerator having less tendency to harden one ofsaid portions of the film, and

' droxide into hardening the other of said portions of the film with themixture.

14. The art of treating light-sensitive film having exposed andrelatively unexposed portions which comprises mixing with apolyhydroxybenzene, sodium hydroxide and a salt of a weak hose in suchproportions as to convert the sodium hyan accelerator having lesstendency to harden the unexposed portions of the film, and hardening theexposed portions ofthe film with the mixture.

15. The art of treating light-sensitive filislliedhaving exposed andrelatively unexpo with a developer ada ted to harden the exposedportion, a fix alkali and an ammonium salt, thereh to term on ammoniaaccelerator, and hardening one of said portions withthe mixture.

16. The art of treating light-sensitive him having exposed andrelatively unex posed portions which. comprises mixing with a polyhydrobenzene, a fixed alkali and ammonium chi oride, thereb to form anammonia accelerator, and her ening said exposed portions with themixture.

Y 17. The art of treating light-sensitive film having exposed andrelatively unexportions "which comprises mixing posed portions whichcomprises mixing with a hardener, sodium hydroxide and ammoniumchloride, thereby to form sodium chloride and ammonium hydroxide, and

'film having exposed and relatively unexposed portions. which oomgrisesmixin with pyrogailic acid, sodium ydroxide an ammonium chloride,thereby to form sodium chloride and ammonium hydroxide, and

hardening said exposed portions with the mixture. I I

,19. A composition for treating lightsensitive film having exposed andunexposed portions which comprises'a developer whose oxidation productis a hardener, sodium h droxide, ammonium chloride, sodium chloride andammonium hydroxide.

'20. A composition for treating lightsensitive film having exposed andunexposed portions droxxgenzene, sodium hydroxid ammonium c oride,sodium chloride an ammonium hydroxide.

Signed by me at Boston, Massachusetts this nineteenth da of August 1922.

LEOiIARD TROLAND.

which comprises a polyhy-

